In recent years aspartame, L-as-partyl-L-phenylalanine methyl ester (also known as APM), and related dipeptide sweeteners have become important artificial sweeteners for a variety of products, especially chewing gum. Aspartame has gained popularity as an artificial sweetener for a number of reasons including its high degree of sweetness estimated to be about 100-160 times the sweetness of sucrose on a weight to weight basis. Aspartame also is perceived to have a more sucrose like taste relative to other available artificial sweeteners such as saccharin which has been perceived to possess a bitter aftertaste.
A high sweetness value would ordinarily reduce the relative amount of sweetener needed to sweeten a comestible such as chewing gum. Although aspartame has a relatively high sweetness value it unfortunately also has exhibited a tendency to undergo hydrolytic degradation in the presence of moisture resulting in subsequent loss of sweetness. This hydrolytic degradation may accelerate at elevated temperatures and specific pH ranges. Aspartame is also known to react with chemicals such as aldehydes and ketones with subsequent loss of sweetness. Some degree of moisture is always present in comestibles and many comestible flavorings contain aldehydes. Additionally, comestibles, especially chewing gum which may be warehoused after manufacture and stocked thereafter, may be exposed to elevated temperatures at various times during their shelf life and/or may not reach the end user until months after produced.
In order to maintain a desired minimum sweetness level throughout their expected shelf life, products sweetened with aspartame can be formulated with excess aspartame to compensate for decomposition of the aspartame over time. For comestibles having a relatively long shelf life, such as chewing gum where the expected shelf life is at least several months, this approach can, however, produce a product which is perceived to be overly sweet if used early in its life. Additionally, adding excess aspartame to compensate for decomposition over time can be expensive due to the cost of aspartame. Another approach to maintaining a desired minimum sweetness level throughout the expected shelf life of a product sweetened with aspartame is to prevent materials such as water and aldehydes from degrading the aspartame so as to extend its shelf life and the corresponding sweetness life of the product containing it.
Numerous attempts have been made and reported in the literature on methods for stabilizing aspartame. Unfortunately none of the methods have completely solved the problem. Perhaps the method of stabilizing aspartame that has been attempted the most is the encapsulation of the aspartame.
U.S. Pat. No. 4,711,784 to Yang discloses encapsulating aspartame with a high molecular weight polyvinyl acetate blended with a hydrophobic plasticizer. According to this patent, aspartame so encapsulated retained 69% of the aspartame after 65 weeks at 20.degree. C.
U.S. Pat. No. 4,590,075 to Wei et al. discloses encapsulating the aspartame in a matrix comprising at least one elastomer; at least one elastomer solvent; at least one wax system and an excipient selected from the group consisting of carbohydrates, polyhydric alcohols and mixtures thereof and optionally containing spherical food particles having microporous channels and a bulk density of 32.4 to about 400.46 kilograms/m.sup.3.
U.S. Pat. No. 4,384,004 to Cea et al. discloses the encapsulation of aspartame with a coating material selected from the group consisting of cellulose, cellulose derivatives, arabino-galactin, gum arabic, polyolefins, waxes, vinyl polymers, gelatin, zein and mixtures thereof.
U.S. Pat. No. 4,139,639 to Bahosky et al. discloses the encapsulation of aspartame with a composition consisting of gum arabic and a specified starch acid-ester.
U.S. Pat. No. 4,673,577 to Patel discloses encapsulating aspartame with food-grade shellac which, according to the patent, forms a substantially impermeable coating and minimizes the degradation of the aspartame to diketopiperazine or its reaction with aldehydes.
In addition to encapsulation, other techniques have been attempted to improve the instability of the aspartame with differing results.
U.S. Pat. No. 4,822,622 to Dokuzovic al. discloses a barrier between the aspartame and the gum base containing the flavoring.
U.S. Pat. No. 4,514,422 to Yang et al. discloses a gum composition containing a maximum of 2% water comprising a substantially anhydrous mixture of a gum base, at least one sugar alcohol and glycerin in an amount of from about 8% to about 18% by weight of the total gum composition. According to the patent, aspartame can be used as an artificial sweetener in this composition.
U.S. Pat. No. 4,774,094 to Carroll et al. discloses stabilizing aspartame by combining it with hydrogenated starch hydrolysate having a cooked moisture content of about 10.+-.6%.
A review of the above-mentioned patents and other literature on the attempts to stabilize aspartame, indicates there is still a need to increase the stability of this artificial sweetener in a variety of products, particularly chewing gum.
It is therefore an object of the present invention to improve the stability of aspartame.
Another object of the present invention is to provide stable compositions containing aspartame that are useful as artificial sweeteners for a variety of comestible products.
Another object of the present invention is to provide a system for reducing the amount of aspartame sweetener needed to sweeten chewing gum and other artificially sweetened products to maintain a minimum desired sweetness level during the expected shelf life of the product by providing aspartame in a form which retards its degradation over time.
Another obJect of this invention is to provide aspartame sweetened chewing gum which retains its sweetness for extended periods of time.
Another object of the present invention is to provide a method for the production of a comestible containing aspartame stabilized against decomposition.
Other objects will become apparent from the ensuing description.